Educational apparatus for demonstrating gravitational effects



Nov. 24, 1959 .EEES 1 B. T. KEEFE EDUCATIONAL APPARATUS FOR DEMON GRAVITATIONAL EFFECTS F1led June 24 1958 United States Patent VO EDUCATIONAL APPARATUS FOR DEMONSTRAT- ING GRAVITATIONAL EFFECTS Bernard T. Keefe, Santa Paula, Calif.

Application June 24, 1958, Serial No. 744,194

8 Claims. (Cl. 35-19) This invention relates to educational apparatus and more particularly to an improved device for demonstrating to students and others basic principles characteristic of falling and projected bodies.

More specifically, it is the object of the invention to provide simple but highly effective apparatus for visually and audibly demonstrating the parallel relationship of the gravitational effect upon freely falling bodies and upon va projected body. The apparatus comprises electrically actuated magnetic retention means for a rst or falling body and a manually actuated launching device operable to lire a second or projectile body directly at the first body together with means for automatically releasing the first body as the projectile leaves the launching device. To accomplish the described synchronization, the launcher is provided with an electrical switch arranged to open the circuit to the magnetic retention means as the projectile leaves the launcher.

Accordingly, it is a primary object of this invention to provide a simple educational apparatus for demonstrating certain gravitational principles effectively.

Another object of the invention is the provision of manually operable launching means for tiring a projectile at a second body in a manner effecting the automatic release of the Second body at the instant the projectile is launched. p

Another object of the invention is the provision of educational apparatus for demonstrating principlesof gravity and utilizing electrically controlled 4synchronizer means for precisely coordinating the release of a freely falling body with the launching of a projectile aimed at the first body.

These and other more specific objects will appear upon reading the following specification and claims and upon considering in connection therewith the attached drawing to which they relate.

Referring now to the drawing in which a preferred embodiment of the invention is illustrated: i

Figure l is a side elevational view of the apparatus incorporating the present invention and showing the projectile at the instant of collision with the freely falling body;

Figure 2 is a view in perspective of the launching device on an enlarged scale'showing the electrical switch in closed position and the projectile launching mechanisrn in relaxed position;

Figure 3 is a side elevational view on an enlarged scale of the adjustable rear sight for the launcher de- Figure 4 is a top plan view of Figure 3; and y Figure 5 is a transverse sectional view through a portion of the supporting means for the rear lower end of the launching device.

Referring to the drawings and vmore particularly to Figures 1 and 2, there is shown a preferred embodiment of the educational apparatus designated generally 10 and including as principal sub-assemblies a projectile launchingldevice 11 and a magnetic retention device 12. The

magnetic retention device in its simplest form comprises an electromagnet 13 having a soft iron core and a simple means, not shown, for supporting the device at a desired height at some distance from launching device 11. The electromagnet has terminal wires 14 and 15 extending therefrom and adapted to be connected with a remote control switch and a source of electrical energy in a manner which will be described presently.

Launching device 11 is here shown as comprising a long main frame 18 provided along its upper side with a guide channel 19 along which the projectile travels while being launched. The launcher frame is adapted to be adjustably supported by a pair of brackets 20 and 21 with the axis of projectile groove 19 accurately aligned with the center of a ball of magnetic material 23 retained magnetically by device V12 so long as the coil of the latter is energized. Preferably at least one of the supporting standards 20, 21 is adjustable both vertically and laterally to facilitate the accurate aiming of the projectile tol be launched. To this end, support 20 comprises a U-shaped clamp 25 adapted to engage over ythe edge of a table top 26 and to be firmly clamped thereto by a thumbscrew threadedly supported in the lower jaw of the clamp. Secured rigidly to the upper jaw of clamp 25 is an upright post 27 having a U-shaped bracket 28 detachably secured to its upper end supporting between the legs thereof across'pin 29 providing a rigidhorizontal support for the forward end of the launcher frame.

Pedestal 21 for the rear endV of the launcher also includes a U-shaped clamp 31 having a thumbscrew 32 carried in its lower jaw for-anchoring the clamp to the edge of table top 26. An upright 33 is xed to the upper jaw of the clamp and supports adjustably therealong a vclamping device 34 provided with a thumbscrew 35 for securing the same in any desired adjusted position. The outer"- end of bracket 34 supports a horizontally disposed threaded rod 36, the latter being detachably secured to bracket 34 by thumbscrew 37. The threaded portion of rod 36 extends through a long slot 38 extending transversely of the rear end of launcher frame 18. Clamping nuts 39, 39 disposed to either lateral edge of the launcher frame permit the launcher to be shifted lengthwise of the rod 36 and to be clamped in any desired position along slot 38. It will also be understood that the rearend of the launcher can be shifted laterally by loosening thumbscrew 37 and shifting rod 36 with respect to bracket 34.

Any suitable meansmay be provided for launching or iiring a projectile from launcher 11, one particularly simple and effective means comprising a tube 40 open at its rear end and closed at its forward end except for a peep sight opening 41. Tube 40 has secured transversely of its top side an inverted stirrup 42. Pivotally connected to openings in downturned ends of stirrup 42 is a wire bail 43 straddling main frame 18 from its lower side and having attached to its midportion a strong coil spring 44. The outer end of this spring is engaged through an opening in a bracket 45 secured to upright 27 by clamp 48. Normally, spring 44'holds launching tube 40 in a position of rest such as that indicated in full lines inV Figures l and 2. It will be understood that the launcher may be manually held in its cocked position at the rear end of projectile guide groove 19 by placing the index and forefnger astride tube 40 and against the forward edges of stirrup 42 and pulling the launcher tube rearwardly stretching lspring 44 to its maximum length. Cooperating with the peephole 41 in the forward end ofv launching tube 40 is a rear sight designated generally 50, this sightbeingadjustably mounted at the rear end launcher frame as by a pair of screws 52. The upturned pointed end 53 of the sight is located in a vertical plane passing through the axis of groove 19. This pointed tip may be accuratelyaligned with the axis of the groove by means of an adjusting screw 54 mounted in the launcher frame and passing through an elongated slot 55 in the midportion of spring 51. Since spring 51 is so shaped as to lie firmly against the underside of screw 54, turning of screw 54 serves to adjust the rear sight upwardly or downwardly depending upon the direction in which the screw is adjusted. Slight loosening of one of the screws 52 permits the spring to be shifted laterally if this should be necessary to realign the pointed end 53 with the axis of groove 19.

A particularly important feature of the apparatus is the provision of an electrical switch designed to be actuated automatically by theprojectile being launched as an incidentrto the firing of the projectile from the forward end of launcher 11, it being understood that this switch controls the activation of electromagnet 12. Desirably, the electromagnet operates at a sufficiently low voltage to avoid hazard to students and uninformed persons. To this end and s ince it is desirable to utilize the customary laboratory electrical' circuits as the source of power, a simple step-down transformer will be understood as housed within casing 60 suitably supported, as on the lower side of launcher frame 18. The primary of this transformer is connected through the usual service cord 61 and plug 62 to the usual power outlet 63 found in any schoolroom or laboratory. The low voltage outlet terminals 64, 65 from the transformer are connected in series circuit with a switch to be described presently and with terminals 14 and 15 of electromagnet 12.

The projectile actuated synchronizing switch is mounted on a pair of rigid brackets 67, 68 secured to the opposite sides of launcher frame 18 in the manner clearly indicated in Figure 2 It is important that these brackets be insulated from one another and this may be accomplished by inserting a sheet of insulating material 69 between bracket 68 and the launcher frame. The switch blade comprises a light copper wire 70 having one end loosely hinged in openings 71 of bracket 67. A sensitive. coil spring 72 has one end supported in an opening of the overturned end 73 of bracket 67 and its opposite end engaged over a U-shaped portion 74 of switch blade 70, the free end of switch blade 70 being adapted to be held captive inra very shallow notch 75 at the upper forward corner of bracket 68. It is pointed out and emphasized that switch blade 7.0, when in its closed position illustrated in Figure 2, is spaced above the bottom of projectile groove 19 by a distance somewhat less than the diameter of the projectile to be used. It is further pointed out that the tension of spring 72 on the switch blade is that slight amount required to hold the blade closed firmly across the opposite contacts of the switch as provided by brackets 67 and 68.

The circuit connectors are such that when the switch blade is closed in the manner described, device 12 is energized and effective to hold a ball of magnetic material 23 captive against the lower end of its core. However, upon theopening of the switch by movement of blade 70 out of notch 75, the circuit to device 12 is broken and ball 23 is instantly released and free to fall by gravity.

To demonstrate that a projectile falls from its path of travel when launched at the same rate as a second and independent body falls from the line of sight of the projectile as launched, irrespective of the spacing between the two bodies at the start and independently of the velocity and angle of launching, the demonstrator or instructorA sets up the two sub-assemblies 11 and 12 in the manner described above. Launcher 11 may belocated at any convenient distance from electromagnet 12 and within the range capabilities of the launcher. VLikewise the angle 'of inclination of the launcher may be selected within a wide range, it only being important that `the axis of projectile travel while in launching groove 19 be accurately aligned with the center of the independent ball 23, as is indicated by the dot and dash line 80 in Figure l. Having made certain that the launcher is so aligned making use of the peepsight 41 in launcher tube 40 and rear sight 50, the apparatus is ready for the demonstration.

A projectile of suitable form, such as the ball 82, is then placed in position at the forward end of launcher tube 40 :and switch blade 70 is closed by placing its free end in notch of bracket 68. The instructor then plac his forefinger and index linger astride the forward edge of stirrup 42 and pulls the launching mechanism to the rear end of groove 19 as ball 82 rolls downwardly behind the closed formed end of tube 40. Firing of the projectile is accomplished by quickly withdrawing the fingers allowing spring 44 to pull launcher tube 40 rapidly along groovev 19 thereby firing projectile 82 from the launcher. As the :advancing projectile engages switch blade 70, the latter is automatically disengaged from notch 75 at the exact instant the projectile is fired from the launcher thereby de-energizing the electromagnet and releasing ball 23. A moment later the two balls collide, as atthe position illustrated in Figure l, thereby conclusively demonstrating that ball 82 has fallen from its aimed path of travel indicated by line 30 through the same vertical distance as the ball 23.

Usually the instructor will wish to confirm these results be repeated firings under the same conditions. Thereafter he can proceed to vary the angle of inclination of the launcher, care being taken that the axis of groove 19 is always in alignment with the center of ball 23 while held captive by electromagnet 12. The two balls 23, 82 will, of course, collide at different distances above the floor depending upon the velocity at which the vprojectile is launched, the angle of inclination of the launcher and its spacing from device 12. However, irrespective of these variables, the balls will always collide.

While the particular educational apparatus for demonstrating principles of gravity herein shown and disclosed in detail is fully capable of attaining the objects and providing the advantages hereinbefore stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and that no limitations are intended to the details of construction or dcsign herein shown other than as defined in the appended claims.A

I claim:

l. A classroom device for demonstrating characteristics of projected and freely falling bodies comprising, electrically controlled retention means, a rst body adapted to be retained stationary by said retention means, launching means for launching a projectile body directly at said first body from a launching position spaced laterally of and on a level below said retention means, and means activated by the launching of said projectile b'ody to activate said retention means to effect the release of said first body simultaneouslywith the launching of said projectile body, whereby said bodies subsequently collide in mid-air to demonstrate certain gravitational laws.

2. A demonstration device of the type defined in claim l characterized in that said retention means comprises an electromagnet operable to release vthe first body upon being de-energized.

3. A demonstration device'of the type defined in claim l characterized in the provision of electric switch means including means arranged in the path of said projectile as it is being launched into space to de-activate said retention means.

4. A demonstration device as defined in claim 3 characterized in that said switch means includes spring-biased easily dislodged retention means positioned in the path of said projectile whilebeing launched and adapted to maintainaneletric circuit to said electrically controlled retention means closed until said projectile is actually launched, whereby the launching of the projectile simul taneously opens said switch means and de-activates said electrically controlled retention means.

5. A demonstration device as deined in claim l characterized in that said projectile launching means comprises elongated channeled means providing a guide for said projectile, means for rigidly supporting said channeled means in an inclined position directed toward said electric retention means, and manually operable spring means for driving a projectile along said channeled means and for launching the same into space along a path aimed directly at said rst body.

6. A demonstration device for tiring a projectile aimed at a magnetically retained body, comprising electromagnetic retention means for detaining a magnetic body so long asrsaid magnetic means is electrically energized,

Va magnetic body adapted to be retained by said retention means, a projectile launching means for tiring a projectile along a path directly at said first body, and an electric circuit for said electromagnetic retention means including a circuit breaking switch therefor located in the path of said projectile as it is being tired and effective to release 6 said first body as the projectile leaves said launching means.

7. A demonstration device as deined in claim 6 characterized by the provision of adjustable support means for said launching means operable to vary the inclination thereof until such inclination lies along an axis passing through said iirst body while held captive by said retention means.

8. A demonstration device as defined in claim 7 characterized in the provision of mechanism slidable along said launching means, spring means or driving said mechanism along said launching means and toward the forward end thereof, said mechanism having a peep sight forwardly of its rear end, and second sight means at its rear end cooperating with said peep sight means as an aid -in adjusting said mechanism in alignment with said magnetic body while said body is held by said electromagnetic retention means.

References Cited in the tile of this patent UNITED STATES PATENTS 1,636,234 Klopsteg July 19, 1927 

